overheating...2010 with 330k miles..47 to 50 mpg still..

Discussion in 'Gen 3 Prius Technical Discussion' started by Herbgh, Nov 15, 2025.

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  1. Herbgh

    Herbgh New Member

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    III
    When draining the system of coolant..I opened the pitcock..on the radiator and nothing came out...330,000 miles...I used water hose to see if I could move some of the accumulated trash out of the bottom...Was partially successful...so went to service mode after replacing pump and thermostat....added coolant til fans came on...Driving home after a few weeks of local driving to test the repair...I got the overheat lite...parked and checked and noticed that the fans were not on... I noticed early on that the cabin heat was very mild...
    so where is the fan thermostat the one at the top and rear of the compartment..near where the hoses lead into the cabin? I opened the air purge valve near there when filling initially...when it overheated that caused the pump and thermostat replacement...I opened the filler cap too soon and the coolant came out and left a chalky white film on that side of the compartment...Engine runs fine , oil clean..no sign of head gasket leak..sooo should I pull the radiator and replace or try to flush or is that an additive ? Or something else...Tnx
     
    #1 Herbgh, Nov 15, 2025
  2. CR94

    CR94 Senior Member

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    Has a stop-leak goo ever been added to the cooling system? That might explain "I opened the pitcock..on the radiator and nothing came out," as well as overheating.
     
    #2 CR94, Nov 22, 2025 at 9:32 PM
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  3. Brian1954

    Brian1954 Senior Member

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    What engine water pump did you buy as a replacement? Toyota OEM or aftermarket?

    Do you have a scanner that you can use to monitor or look at the engine coolant temperature? The reason I ask is because the overheating warning light on the dashboard can be activated by high engine coolant temperature, or it can also be activated by high coolant temperature from the exhaust heat recovery system. Read this thread, https://priuschat.com/index.php?posts/3549096
     
    #3 Brian1954, Nov 22, 2025 at 10:40 PM
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  4. BiomedO1

    BiomedO1 Senior Member

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    Dried coolant shouldn't leave a "white chalky film" - I'm guessing someone used a stop-leak product in your cooling system. There's no filter in your cooling system and there shouldn't be any crud on the bottom of your radiator. Did you keep up with OEM recommended coolant change intervals?
    Another stupid question; did you change the engine or inverter coolant pump? Engine coolant pump is on the passenger side; inverter pump is on the drivers side.
    You need to verify, which over-temperature sensor is being tripped.

    Good Luck.....
     
    #4 BiomedO1, Nov 23, 2025 at 12:48 AM
    Last edited: Nov 23, 2025 at 12:53 AM
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